A treatment agent for treating the surface of a metal has been used in broad fields such as automobiles, home electric appliances, architecture, foods, medicines, etc., in particular, it is useful for improving interlaminar adhesiveness between a metal material such as aluminum, magnesium, copper, iron, zinc, nickel or an alloy thereof, and various resin coating layers provided on the surface thereof, solvent resistance of the resin coating layer and corrosion resistance of the metal material.
Examples of the metal surface treatment agent of the prior art include an aqueous treating solution using trivalent chromium (Patent Literature 1). This treating agent can be used without using hexavalent chromium having high toxicity, but when it is exposed to high temperature environment, oxidation of chromium proceeds to generate hexavalent chromium. Thus, there are problems of environment.
In view of such a background, non-chromium treating agents have been investigated variously until now. In particular, in the uses which require corrosion resistance, adhesiveness with a paint, a resin or the like, there are problems that the performances are insufficient. Therefore, trivalent chromium treating agents which are harmful to human body or environment have yet been used.
Among these, a package for a lithium secondary battery, a film-attached tab lead member and the like are required to have severe adhesion reliability such as electrolyte resistance, HF resistance and the like, in the adhesion of a polyolefin film such as polyethylene and polypropylene with a metal such as aluminum, copper and nickel, and various non-chromium type techniques have been published (Patent Literature 2). However, it is the present status that the non-chromium type treating agents are inferior in surface treatment performances to those of the conventional trivalent chromium type treating agent.